This invention relates to a vehicle suspension apparatus with a rolling control function of suppressing the rolling of the vehicle when the vehicle is making a turn or a vehicle height control function of controlling the vehicle height to a desired height.
A well-known vehicle suspension apparatus with the rolling control function or vehicle height control function as noted above, comprises suspension units each provided for each wheel and having an air spring chamber, compressed air supply means for supplying compressed air to the air spring chambers of the individual suspension units through an air supply control valve, and exhausting means for exhausting compressed air from the air spring chambers of the suspension units through an exhaust control valve. The compressed air is supplied from a compressor or a reservoir tank where compressed air produced by the compressor is stored.
In such a suspension apparatus, however, the compressor, which constitutes a comparatively high load, is driven even at the time of or immediately after the start of the engine so long as the pressure in the air spring chambers or in the reservoir tank is lower than a predetermined level. Therefore, a considerable time is passed until the pressure of the engine oil of the engine which drives the compressor exceeds a predetermined level. This is undesired from the standpoint of the engine lubrication. In addition, the idling of the engine cannot be stabilized. Further, when the compressor which consumes comparatively high electric energy is driven concurrently with the starter motor for starting the engine, it is liable that the revolving rate of the starter motor is not increased sufficiently so that a smooth engine start cannot be obtained particularly when it is cold.